1. Field of the Invention
The present invention relates to a light source unit, a projection apparatus, and a projection method suitable for a projector or the like.
2. Description of the Related Art
Jpn. Pat. Appln. KOKAI Publication No. 2004-341105 (hereinafter, Patent Document 1), for example, discloses a technique including a light-emitting diode or semiconductor laser to emit ultraviolet light, and a color wheel which has a fluorescent layer formed on the back side for emitting visible light corresponding to each of red, green, and blue light by radiating ultraviolet light and has a visible light reflection film formed on the front side close to a light source, having characteristics to transmit ultraviolet light and reflect visible light.
In the technique disclosed in Patent Document 1, when a fluorescent substance is generated by using excitation light, according to the properties of the fluorescent substance, the fluorescent substance is saturated when the excitation light per unit area radiated to the fluorescent substance exceeds a certain value, and the luminous efficiency of the fluorescent substance may be suddenly reduced.
Despite this, Patent Document 1 does not mention the excitation light per unit area radiated to the fluorescent substance and saturation of fluorescent substance. Therefore, there is a problem that the absolute quantity of light becomes insufficient if excitation light is decreased to avoid saturation of the fluorescent substance, and the luminous efficiency of the fluorescent substance is decreased if excitation light is increased to obtain a sufficient absolute light quantity.